Different Trends in Antarctic Temperature and Atmospheric CO2 During the Last Glacial

We analyze the past 67,000 years of climate using Antarctic ice-core records to constrain the mechanisms involved in (a) the "bipolar seesaw" relationship between Greenland and Antarctic surface temperature variations, and (b) mechanisms of millennial-scale atmospheric CO2 concentration variations. Specifically, we determine for each Greenland Stadial the rate of Antarctic temperature and atmospheric CO2 rise. We find that Antarctic warming rates significantly decrease as the climate cools during the glacial period, whereas the rate of atmospheric CO2 rise does not significantly change. Also, we find that the rates of Antarctic warming and atmospheric CO2 rise are both insensitive to whether a given stadial contains a Heinrich event. These results challenge the view that a single Southern-Ocean-based mechanism dominates the observed glacial variability in Antarctic temperature and atmospheric CO2. Instead, our results are consistent with an important contribution of low- and mid-latitude processes to millennial-scale atmospheric CO2 changes.